I don't expect huge open world DEs to ever become as enjoyable as the players want for a very simple reason. If the DE is worth doing, whether for loot or sheer awesomeness factor, then it will be swamped and you'll feel like just another zergling in the swarm. The DE system shines best on the events that can comfortably be done with 3-8 players. I love coming across one of those and seeing a small number of other players, or even starting it solo and have 1-3 ride in to support me before it gets ugly.